Electronic governor



Dec. 5, 1967 D. s. DENNIS 3,356,081

ELECTRONIC GOVERNOR Filed Dec. 21,- 1964 i i I g'wr R g i i r I I-I I INVENTOR 4901/10 5 flew/71$ ATTORNEY Patented Dec. 5, 1967 3,356,081 ELECTRONIC GOVERNOR David S. Dennis, Chesterfield, 1nd,, assignor to General Motors Corporation, Detroit, Mich a corporation of Delaware Filed Dec. 21, 1264, Ser. No. 419,997 4 Claims. (Cl. 1231tl2) This invention relates to an electronic governor for an engine and more particularly to an electronic governor for regulating the speed of an internal combustion engine of a motor vehicle.

It is common practice to provide the internal combustion engines of vehicles such as buses and trucks with a maximum speed governor to prevent damage to the engine by inadvertent overspeeding as well as to limit the maximum vehicle speed. Many of the prior art speed regulating systems utilize a vacuum powered servo unit for controlling the engine throttle valve. When vacuum is introduced, the unit causes the engine throttle valve to be moved toward the closed throttle position thereby preventing the engine from overspeeding.

In accordance with the present invention, an electronic control circuit is provided for controlling the admission of vacuum to the servo unit. More particularly, a hot wire controlled valve mechanism is utilized for controlling the admission of vacuum to the servo unit and a monostable multivibrator responsive to both actual engine speed and the desired governing speed controls the application of current to the hot wire. When current flows through the hot wire, vacuum is admitted to the servo unit which is then operable to close the throttle valve.

A more complete understanding of the present invention may be had from the following detailed description which should be read in conjunction with the drawing in which:

FIGURE 1 is a sectional view showing the engine throttle valve control mechanism;

FIGURE 2 is a sectional view of the heat sensitive valve mechanism of the present invention;

FIGURE 3 is a schematic diagram of the control circuit of the present invention.

Referring now to the drawing and initially to FIGURE 1, the vehicle engine is provided with an engine air intake in which is mounted a throttle valve 12 on a rotatable throttle valve shaft 14 passing transversely through the intake 10. The shaft 14 is secured to a lever 16 which has one end of a spring 18 attached thereto. The other end of the spring 18 is secured to a relatively immovable portion of the engine. The spring 18 is preferably of the tension type and tends to hold the throttle valve 12 in the open position.

A rod 20 connects the lever 16 to a diaphragm 22 of a vacuum powered servo unit generally designated 24. The chamber 26 of the unit 24 is at substantially atmospheric pressure at all times. The chamber 28 of the unit 24 is open to the atmosphere through a connection to the opening 30 as explained with regard to FIGURE 2 and is also open to engine intake manifold vacuum through the orifice 32. If the chamber 28 is closed to the atmosphere, the air in chamber 28 will be evacuated into the intake manifold through the orifice 32 causing the diaphragm 22 to move in the direction to close the throttle valve 12.

Referring now to FIGURE 2, a device for controlling the pressure in chamber 28 and consequently the position of the throttle valve 12 is shown and includes a housing 33 providing a chamber 34 which is vented to the atmosphere through an orifice 36. An opening 38 in the housing 33 is connected by a conduit (not shown) to the opening 30 so that the pressure in chamber 28 is the same as the pressure in chamber 34. A spring 40 carrying a valve element 42 is normally biased to a position such that orifice 36 will be sealed. A hot wire 44 is secured to the post 46 and when cold, urges the valve element 42 to an open position. Connectors 48 and 58 provide a path for current flow through the hot wire 44.

Referring now to FIGURE 3, there is shown a circuit for controlling the current flow through the hot wire 44 to position the valve element 42 thereby controlling the air bleed to chamber 28 of the servo unit 24. The circuit includes a monostable multivibrator generally designated 52 which is adapted to be triggered by a trigger circuit generally designated 54. The trigger circuitry 54 may be any one of a number of well-known engine speed sensing circuits which provide an electrical signal, the frequency of which is proportional to the speed of the engine. The output of the multivibrator is fed to a filter network 56 for obtaining an average voltage which is compared with a reference voltage established by voltage dividing resistors 58 and 60. The difference between the average voltage output of the multivibrator 52 and the D.-C. voltage established by the resistors 58 and 68 controls a D.-C. amplifier generally designated 62 and consequently, the amount of current flow through the hot wire 44.

The monostable multivibrator 52 includes a pair of transistors 64 and 66 which have their emitters grounded and their collectors connected to a battery 68 through resistors 70 and 72, respectively. Resistor 74 connects the collector of transistor 60 to the base of transistor 64 and resistor 76 connects the base of transistor 64 to ground. A capacitor 78 is connected between the collector of transistor 64 and the base of transistor 66. A fixed resistor 80 and a variable resistor 82 are connected between the base of transistor 66 and the battery 68.

The output of the multivibrator 52 is taken from the collector of transistor 66. The waveform at this point is essentially square. The pulse width or unstable time of the multivibrator 52 is primarily determined by the discharge time constant of capacitor 78 and resistors 80 and 82. The resistor 82 is variable to adjust the desired governing speed. Since the trigger pulses applied to the input of the multivibrator 52 are related in frequency to the speed of the engine, the output pulse train of the multivibrator 52 will have a pulse width related to the desired governing speed and a pulse rate related to the actual speed of the engine. Since the pulse width is constant at a particular governing speed, it will be understood that the average output voltage of the multivibrator 52 varies as the frequency of the applied trigger pulses. The filter network 56 comprises resistors 84 and 86 and capacitor 88 and filters the pulsating D.-C. voltage from the multivibrator 52 to .provide an average output voltage, which is fed to the D.-C. amplifier 62 which includes tranisstors 96 and 92. The emitter of transistor 90 is connected to the junction of the voltage dividing resistors 58 and 6t and the collector of transistor 90 is connected to the base of transistor 92. The hot wire 44 is connected across the battery 68 through the emitter-collector path of the transistor 92. A resistor 94 connects the emitter of the transistor 92 to the base of the transistor 90 for gain stabilization.

The operation of the electronic governor is as follows. When the actual speed of the engine, as evidenced by the frequency of the output pulses from the trigger circuitry 54, is below the desired governing speed, as set by the resistor 82 in the multivibrator 5 the average output voltage of the multivibrator 52 appearing at the base of tran sistor 90 will be less than the voltage established at the emitter of transistor 90 by the voltage dividing resistors 58 and 60. The transistor 90 will therefore be non-conductive as will the transistor 92. Since the transistor 92 is non-conductive, no current flows through the hot wire 44; and consequently, the orifice 36 is open, placing atmospheric pressure on both sides of the diaphragm 22 and allowing the spring 18 to maintain the throttle valve 12 in an open position.

As the speed of the engine increases, the input trigger frequency of the multivibrator 52 will increase; and consequently, the average output voltage of the multivibrator 52 will approach the D.-C. voltage established by the resistors 53 and 60. When the engine reaches the desired governing speed, the D.-C. output voltage of the multivibrator 52 is sufiicient to render transistor 90 conductive turning on the transistor 92 and allowing current to pass through hot wire 44. The amount of current which flows through the hot wire 44 determines the position of the valve element 42 and, consequently, the position of the throttle valve 12. If the speed of the engine exceeds the desired governing speed, the current through the hot wire 44 increases, allowing the valve element 42 to move in a direction to seal orifice 36. This, in turn, introduces increasing vacuum in chamber 28, tending to close the throttle valve 12 reducing the speed of the engine. As engine speed is reduced, the current flowing in the hot wire 44 is reduced until a balance between the speed of the engine and current flow in the hot wire 44- has been reached which will maintain the engine at the desired governing speed.

While the invention has been described with regard to a preferred embodiment thereof, this should not be construed in a limiting sense. Modifications and variations will now occur to those skilled in the art. For a definition of the invention, reference should be made to the appended claims.

I claim:

1. In combination with an engine having throttle means biased toward an open position and movable toward a closed position by a vacuum powered servo system, valve means actuated by passage of current through a hot wire for controlling said servo system, means operatively connected with said engine for developing an input signal related to the speed of said engine, a monostable multivibrator responsive to said input signal for developing a pulsating output signal having a pulse width proportional to a predetermined governing speed and a pulse rate related to the frequency of said input signal, filtering means responsive to the output of said multivibrator for developing an average output signal, the average output signal of said multivibrator exceeding a predetermined level when the speed of said engine reaches said predetermined speed, switching amplifier means adapted to connect said hot wire to a source of current when the average ouput level of said multivibrator exceeds said predetermined level.

2. In combination with an engine having throttle means biased toward an open position and a pneumatic power system for moving the throttle means toward a closed position in response to the introduction of vacuum to said system, a source of vacuum, valve means for controlling the introduction of vacuum from said source to said system, a hot wire actuator for controlling said valve means, a source of electrical current, means operatively associated with said engine for developing an input signal related to the speed of said engine, a monostable multivibrator responsive to said input signal for developing a pulsating output signal having a pulse width proportional to a predetermined governing speed and a pulse rate related to the frequency of said input signal, filtering means responsive to the output of said multivibrator for developing an average output signal, said average output signal exceeding a predetermined level when the speed of said engine reaches said predetermined governing speed, switching amplifier means adapted to connect said hot wire actuator to said source of current when said average output level exceeds a predetermined level.

3. An electronic governor for an internal combustion engine of a motor vehicle, said engine having throttle means biased toward an open position, said governor comprising control means responsive to heat generated by electrical current flow for moving said fuel control means toward a closed position, means operatively associated with said vehicle for developing an input signal having a frequency proportional to the actual speed of said vehicle, a monostable multivibrator responsive to said input signal and having an unstable operating time proportional to a desired governing speed for developing a pulsating output signal, means responsive to said output signal for developing an average output signal, switching amplifier means for connecting said heat sensitive control means to a source of current in response to said average output signal exceeding a predetermined value.

4. A governor for an engine having fuel control means movable between an open and closed position and normally biased toward one of said positions, pressure responsive actuator means for moving said fuel control means toward said other position, valve means for controlling the pressure in said actuator means, said valve means including a valve port, a valve member to open and close said port, spring means normally biased in said valve member in a first direction, thermally responsive valve control means comprising a heat expansible element operative upon said spring means and normally exerting a force on said spring means in a direction opposite to said first direction, circuit means comprising means operatively associated with said engine for developing an input signal having a frequency proportional to the actual speed of said engine, multivibrator means responsive to said input signals for developing an output signal having a pulse width related to a desired governing speed and a pulse rate related to the frequency of the input signal, means responsive to said output signal for developing an average output signal and amplifier means connected with said heat expansible element and responsive to said average out-put signal exceeding a predetermined value.

References Cited UNITED STATES PATENTS 2,013,728 9/1935 Fitzgerald 25l1l X 2,454,659 11/1948 Leonard 123-102 X 3,020,897 2/1962 Shigenobu 3l7l48.5 X 3,070,185 12/1962 Fales 82.l

MARK M. NEWMAN, Primary Examiner.

RALPH D. BLAKESLEE, Examiner. 

3. AN ELECTRONIC GOVERNOR FOR AN INTERNAL COMBUSTION ENGINE OF A MOTOR VEHICLE, SAID ENGINE HAVIG THROTTLE MEANS BIASED TOWARD AN OPEN PSITION, SAID GOVERNOR COMPRISING CONTROL MEANS RESPONSIVE TO HEAT GENERATED BY ELECTRICAL CURRENT FLOW FOR MOVING SIAD FUEL CONTROL MEANS TOWARD A CLOSED POSITION, MENS OPERATIVELY ASSOCIATED WITH SAID VEHICLE FOR DEELOPING AN INPUT SIGNAL HAVING A FREQUENCY PROPORTIONAL TO THE ACTUAL SPEED OF SID VEHICLE, A MONOSTABLE MULTIVIBRATOR RESPONSIVE TO SAID INPUT SIGNAL AND HAVING AN UNSTABLE OPERATING TIME PROPORTIONAL TO A DESIRED GOVERNING SPEED FOR DEVELOPING A PULSATING OUTPUT SIGNAL, MEANS RESPONSIVE TO SAID OUTPUT SIGNAL FOR DEVELOPING AN AVERAGE OUTPUT SIGNAL, SWITCHING AMPLIFIER MEANS FOR CONNECTING SAID HEAT SENSTIVE CONTGROL MEANS TO A SOURCE OF CURRENT IN RESPONSE TO SAID AVERAGE OUTPUT SIGNAL EXCEEDING A PREDETERMINED VALUE.
 4. A GOVERNOR FOR A ENGINE HAVING FUEL CONTROL MEANS MOVABLE BETWEEN AN OPEN AND CLOSED POSITION AND NORMALLY BIASED TOWARD ONE OF SID POSITIONS, PRESSURE RESPONSIVE ACTUATOR MEANS FOR MOVING SAID FUEL CONTROL MEANS TOWARD SAID OTHER POSITION, VALVE MEANS FOR CONTROLLING THE PRESSURE IN SAID ACTUATOR MEANS, SAID VALVE MEANS INCLUDING A VALVE PORT, A VALVE MEMBER TO OPEN AND CLOSE SAID PORT, SPRING MEANS NORMALLY BIASED IN SAID VALVE MEMBER IN A FIRST DIRECTION, THERMALLY RESPONSIVE VALVE CONTROL MEANS COMPRISING A HEAT EXPANSIBLE ELEMENT OPERATIVE UPON SAID SPRING MEANS AND NORMALLY EXERTING A FORCE ON SAID SPRING MEANS IN A DIRECTION OPPOSITE TO SAID FIRST DIRECTION, CIRCUIT MEANS COMPRISING MEANS OPERATIVELY ASSOCIATED WITH SID ENGINE FOR DEVELOLPING AN INPUT SIGNAL HAVING A FREQUENCY PROPORTIONAL TO THE ACTUAL SPEED OF SAID ENGINE, MUKTIVIBRATOR MEANS RESPONSIVE TO SAID INPUT SIGNALS FOR DEVELOPING AN OUTPUT SIGNAL HAVING A PULSE WIDTH RELATED TO A DESIRED GOVERNING SPEED AND A PULSE RATE RELATED TO THE FREQUENCY OF THE INPUT SIGNAL, MEANS RESPONSIVE TO SAID OUTPUT SIGNAL FOR DEVELOPING AN AVERAGE OUTPUT SIGNAL AND AMPLIFIER MEANS CONNECTED WITH SAID HEAT EXPANSIBLE ELEMENT AND RESPONSIVE TO SAID AVERAGE OUTPUT SIGNAL EXCEEDING A PREDETERMINED VALUE. 